Outdoor lighting systems have commonly been used to illuminate streets, parking lots, sidewalks, parks, and other public areas. However, many outdoor lighting systems result in unwanted glare, light trespass, energy waste, sky glow, and other generally unwanted light pollution. Many outdoor lighting systems also produce spectral pollution; i.e., unwanted or hazardous effects resulting from the color spectrum emitted from the lighting system. Amongst other things, spectral pollution can have detrimental environmental effects on plant and animal species; for example, nocturnal mammals, migratory birds, and sea turtles. Roadway lighting and security lighting along the coastline of Florida, for example, have been shown to result in sometimes catastrophic reductions in the breeding success of several species of sea turtles. For example, certain lights can inhibit adult female turtles from coming ashore to lay their eggs, and also lure newly hatched turtles inland rather than to the open sea.
The American Astronomical Society and the International Astronomical Union recommend several solutions for alleviating light pollution or light trespass. The recommendations include controlling the emitted light via light fixture design and placement, taking advantage of timers and occupancy sensors, using ultraviolet and infrared filters to remove non-visible radiation, and using monochromatic light sources such as low-pressure sodium (LPS) lamps for roadway, parking lot, and security lighting. Unfortunately, the recommendations each have their limitations and disadvantages. For example, while the use of an amber monochromatic light may minimize unwanted environmental effects, amber monochromatic light compromises color rendering and provides inadequate viewing conditions for certain mission-critical circumstances. Further, solutions for alleviating light pollution or light trespass are not always effective in alleviating spectral pollution.
What is needed is a lighting system that is efficient, cost-effective, and minimizes spectral pollution, while providing adequate lighting and color rendering for varying circumstances.